At the lower intensity regimes encountered in [1]}, very different dynamics are expected. The laser pulse generates non-equilibrium charge carriers through a combination of multi-photon absorption, Zener breakdown and avalanche processes, the relative strengths of which are highly non-linear with respect to the focal intensity [2]} [3]} [4]} [5]}. Following the pulse, carriers thermalise rapidly through carrier-carrier scattering to a temperature much higher than the lattice [6]}. Scattering with optical and acoustic phonons follows on tens of picosecond timescales such that the excess energy is dissipated into the lattice and the two approach a quasi-equilibrium temperature which decays away through thermal diffusion over several microseconds [7]} [8]} [9]}. The non-equilibrium nature of this system allows for some unusual states of matter including dense excitonic states and at a low enough temperature, condensation into an electron-hole liquid [6]}. Such states are long lasting and eventually decay through recombination processes.
